1. Field of the Invention
The present invention relates to consolidating unconsolidated subterranean formations. More particularly, the present invention relates to improved resin compositions and their use in consolidating unconsolidated subterranean formations to prevent the production of particulates along with formation fluids.
2. Description of the Prior Art
Hydrocarbon wells are often located in subterranean zones that contain unconsolidated particulate matter that can migrate out with oil, gas, water, and/or other fluids produced by the wells. The presence of particulate matter, such as sand, in produced fluids is disadvantageous and undesirable in that the particulates may abrade pumping and other producing equipment and reduce the fluid production capabilities of the producing zones. Unconsolidated subterranean zones include those which contain loose particulates that are readily entrained by produced fluids and those wherein the particulates making up the zone are bonded together with insufficient bond strength to withstand the forces produced by the production of fluids through the zones.
One method of controlling loose sands in unconsolidated formations involves placing a filtration bed of gravel near the wellbore in order to present a physical barrier to the transport of unconsolidated formation fines with the production of hydrocarbons. Typically, such so-called “gravel packing operations” involve the pumping and placement of a quantity of a desired particulate into the unconsolidated formation adjacent to the wellbore. Such packs may be time consuming and expensive to install.
Another method used to control loose sands in unconsolidated formations involves consolidating unconsolidated subterranean producing zones into hard permeable masses by (1) pre-flushing the formation, (2) applying a hardenable resin composition, (3) applying a spacer fluid, and (4) applying an after-flush fluid containing an external catalyst activation agent to remove excess resin from the pore spaces of the formation sand and to cause the resin to set. Such multiple-component applications, however, often result in uncertainty and create a risk for undesirable results. For example, when an insufficient amount of spacer fluid is used between the application of the hardenable resin and the application of the external catalyst, the resin may come into contact with the external catalyst in the wellbore itself rather than in the unconsolidated subterranean producing zone. This may be very problematic. When resin is contacted with an external catalyst an exothermic reaction occurs that may result in rapid polymerization. The polymerization may damage the formation by plugging the pore channels, may halt pumping when the wellbore is plugged with solid material, or may even result in a down hole explosion as a result of the heat of polymerization. Also, using these conventional processes to treat long intervals of unconsolidated regions may not be practical due to the difficulty in determining if the entire interval that has been treated with both the resin and the activation agent.
Another problem encountered in the use of hardenable resin compositions is that the resins have heretofore had very short shelf lives. The shelf lives of some resins once mixed have been as short as about four hours or less. Such a short-shelf life can lead to costly waste if the operation using the resin is postponed after the resin is mixed.